In a boat propelled by jetting water pressurized and accelerated by a water jet pump, as thrust is decreased to a state in which a throttle valve is fully closed (an off-throttle state) during operation, the cornering performance is deteriorated. For technique for solving this problem, technique for controlling the speed of an engine for driving the water jet pump using handlebar off-steering information as a trigger heretofore exists.
For example, as described in Japanese Patent No. 2001-329881 and Japanese Patent No. 2002-87390, the cornering performance can be improved by increasing engine speed based upon steering angle and boat speed.
However, in the conventional examples, as shown in FIG. 8, the target engine speed of an off-throttle steering system (OTS) may be unable to be achieved depending upon a throttle angle. For example, in an example shown in FIG. 8, in case a throttle angle is 5°, engine speed can be enhanced up to the target engine speed of OTS which is slightly higher than engine speed in idling. However, as engine speed cannot be enhanced up to the target engine speed of OTS in case a throttle angle is 3°, control over steering may be difficult. Therefore, it would be beneficial to measure steering. Such a device would preferably be reliable, light weight, and inexpensive.